IBM F50 RS/6000 7025 - Manual (Page 162)

Installing Memory
The memory in your system is installed on memory cards, you can have up to two
memory cards installed. The memory DIMMs are installed in identical matched pairs,
that is, they must be installed across from each other. For example, if you have a
memory DIMM installed in J1 you must have an identical memory DIMM installed in
J2. In order for you to add or remove memory to or from an existing memory card,
you must remove the memory adapter card from the system.
5-18 IBM RS/6000 7025 F50 Series User's Guide